Multiple wavelengths generation utilizing nonlinear optics of four wave mixing
The response turns from linear to nonlinear when high intensity waves propagate in optical fibers, causing the emergence of nonlinear phenomena such as stimulated Brillouin scattering (SBS) and four wave mixing (FWM). While that phenomena cause optical communication systems to deteriorate, they are...
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| Format: | Thesis |
| Published: |
2014
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/7896/ http://eprints.uthm.edu.my/7896/1/noran_azizan_cholan.pdf |
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| Summary: | The response turns from linear to nonlinear when high intensity waves propagate in
optical fibers, causing the emergence of nonlinear phenomena such as stimulated
Brillouin scattering (SBS) and four wave mixing (FWM). While that phenomena
cause optical communication systems to deteriorate, they are nevertheless usehl for
certain applications such as in multiple wavelengths generation. This dissertation
presents experimental work that involves the manipulation of FWM in the
developments of lasers and cascades. Four main research studies are successhlly
demonstrated in efforts to improve the performance of FWM-based lasers and
cascades. The first study is related to multiwavelength BEFLs. Despite the advantage
of wide tunability, they unfortunately suffer from the laser output flatness due to the
nature of cascaded SBS processes. In this work, FWM in an optical fiber is applied to
the laser lines of a multiwavelength BEFL through the incorporation of residual
waves in order to make the output flat. Comparisons between the BEFL with and
without the assistance of FWM suggest the effectiveness of the proposed technique.
With the assistance of FWM, the uniformity or flatness records a 3.73 dB
improvement as compared to the case without the assistance of FWM when the
Brillouin pump is set to 1550 nrn. The second research work is related to an
experimental study on the residual waves of multiwavelength BEFLs. Experimental
results suggest that the properties of residual waves are influenced by FWM.
Multiple FWM processes in fibers are believed to cause the output power of the
residual waves to grow gradually and the value of optical-signal-to-noise ratio to be
lower due to the power sharing basis of FWMprocesses. The third research work, on
the other hand, is aimed to improve continuous tunability of erbium-doped fiber
lasers (EDFLs) in which the stability is obtained from multiple FWM processes in
optical fibers. With the incorporation of tunable bandpass filters in the laser cavity, a
proposed dual wavelength EDFL can achieve continuous wavelength spacing from
0.52 nm to 22.78 nm, limited only by the gain bandwidth of the erbium-doped fiber
amplifier and the linewidth of filters. In the fourth research work, FWM cascades
without external laser sources and modulators is proposed in a bid to reduce the
complexity of the system. The need for laser sources is catered by a dual wavelength
EDFL which acts as an intracavity pump, while the requirement for pump
modulators for SBS suppression is tackled by the broad linewidth of the EDFL. In
summary, four research studies that are related to FWM in generating multiple
wavelengths are experimentally demonstrated in this thesis. The first two studies
focus on improvements in BEFLs, while the third and fourth study is for
enhancements in EDFLs and FWM cascades respectively. All the four studies are
found to be effective in elevating the performances and understanding of FWMbased
lasers and cascades to fwther heights. |
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